1. Field of the Invention
The present invention relates generally to an apparatus for receiving broadcasting signals, and more particularly, is directed to an improvement in a broadcasting signal receiving apparatus which is operative to receive a broadcasting signal carrying synchronous data, control information data and plural groups of program information data and to reproduce desirous program information based on a group of data selected from the plural groups of program information data carried by the broadcasting signal received thereby.
2. Description of the Prior Art
Although an analog audio broadcasting system which includes an amplitude-modulated (AM) audio broadcasting system in which audio signals are transmitted in the form of an AM audio information signal and a frequency-modulated (FM) audio broadcasting system in which audio signals are transmitted in the form of a FM audio information signal, has been put to practical use for a long time in the field of audio broadcasting, there has been recently proposed to introduce a digital audio broadcasting system in which audio signals are transmitted in the form of a digital audio information signal for the purpose of improving quality of audio information transmitted or received in the system. Especially, in the region of Europe, the digital audio broadcasting system called xe2x80x9cDABxe2x80x9d has been already put to practical use in some countries.
The digital audio information signal transmitted from a broadcasting station under the digital audio broadcasting system is called a digital audio broadcasting signal. The digital audio broadcasting signal carries not only audio information data forming a digital audio signal but also service information data representing service information, such as weather forecast, traffic information and so on, and further carries control information data which are necessitated for reproducing the digital audio signal based on the audio information data and the service information based on the service information data on the receiving side. Then, the digital audio broadcasting signal is a modulated wave signal obtained by modulating a carrier wave signal with digital data, such as audio information data, service information data, control information data and so on, in accordance with the Orthogonal Frequency Division Multiplexing (OFDM) system and the digital data transmitted by the digital audio broadcasting signal is composed of a series of frame units, each of which is called a transmission frame.
The transmission frame has a time duration of, for example, 24 ms and contains 77 segmental periods each named Symbol and identified with Symbol 0 to Symbol 76, respectively, as shown in FIGS. 1A to 1C. The Symbol 0 is a null Symbol where the modulated wave signal does not exist in actual fact. The Symbol 1 is a reference Symbol for synchronization. The Symbol 0 which is the null Symbol corresponds to about 324 xcexcs and each of the Symbol 1 to the Symbol 76 corresponds to about 312 xcexcs.
A channel named Synchronous Channel is allocated to the Symbol 0 and the Symbol 1, a channel named Fast Information Channel (FIC) is allocated to the Symbol 2 to the Symbol 4 following the Symbol 1, and a channel named Main Service Channel (MSC) is allocated to the Symbol 5 to the Symbol 76 following the Symbol 4, as shown in FIGS. 1A and 1B. In the Synchronous Channel, synchronous information data DRS are transmitted by the Symbol 1. The MSC is composed of a series of frames each named Common Interleaved Frame (CIF) for transmitting composite data DXD constituted by the audio information data and the service information data. The FIC is composed of a series of blocks each named First Information Block (FIB). The FIB contains a couple of portions of an FIB data field and an error checking word, and the FIB data field is composed of a series of groups each named Fast Information Groups (FIG). The FIC thus formed transmits control information data DCD representing multiplex configuration information (MCI) and other information.
Each of the audio information data and the service information data constituting the composite data DXD transmitted by the MSC contains various groups of program information data, such as program information data 1 to program information data N+M+2, as shown in FIGS. 1B and 1C.
Such a digital audio broadcasting signal as described above is received by use of a digital audio broadcasting signal receiver. In the digital audio broadcasting signal receiver, each of the digital audio broadcasting signals transmitted respectively from a plurality of broadcasting stations is received selectively through a tuning operation by a tuner and the received digital audio broadcasting signal is subjected to radio frequency (RF) amplification, frequency conversion, intermediate frequency (IF) amplification, digital demodulation, decoding processing and so on so that audio information data, service information data and control information data are obtained. Then, the audio information data or the service information data are further subjected to program selection, decoding processing and so on so that digital audio signals or service data are reproduced as desirous program information.
When the aforementioned reception of the digital audio broadcasting signal by the digital audio broadcasting signal receiver is practically carried out, usually one of plural groups of program information data contained in the audio information data or the service information data is selected and desirous program information is reproduced based on the selected program information data which are intermittently obtained. Accordingly, the digital audio broadcasting signal receiver is preferably required to be put in normal operation only in intermittent periods in each of which the desirous program information is reproduced based on the selected program information data.
However, in practice, a digital audio broadcasting signal receiver proposed previously is usually put in normal operation in not only the intermittent periods in each of which the desirous program information is reproduced based on the selected program information data but also other periods in each of which program information other than the selected program information is reproduced. This means that the digital audio broadcasting signal receiver proposed previously brings about power consumption in the periods in each of which program information other than the selected program information is reproduced and therefore the digital audio broadcasting signal receiver is not preferably required to be put in normal operation, in the same manner as in the intermittent periods in each of which the desired program information is reproduced based on the selected program information data. Since power consumption per unit time duration in the digital audio broadcasting signal is relatively large, the power consumption brought in the digital audio broadcasting signal receiver in such a manner as mentioned above excludes substantially the digital audio broadcasting signal receiver proposed previously from practical battery operation. That is, it is very difficult for the digital audio broadcasting signal receiver proposed previously to be formed in a portable type which is able to operate for a relatively long time with power supply from a battery.
Accordingly, it is an object of the present invention to provide an apparatus for receiving broadcasting signals, by which a broadcasting signal carrying synchronous data, control information data and plural groups of program information data is received and desired program information is reproduced based on a group of data selected from the plural groups of program information data carried by the received broadcasting signal, and which avoids the aforementioned disadvantages encountered with the prior art.
Another object of the present invention is to provide an apparatus for receiving broadcasting signals, by which a broadcasting signal carrying synchronous data, control information data and plural groups of program information data is received and desired program information is reproduced based on a group of data selected from the plural groups of program information data carried by the received broadcasting signal, and in which power consumption is effectively reduced so as to make it possible to introduce practical battery operation.
A further object of the present invention is to provide an apparatus for receiving broadcasting signals, by which a broadcasting signal carrying synchronous data, control information data and plural groups of program information data is received and desired program information is reproduced based on a group of data selected from the plural groups of program information data carried by the received broadcasting signal, and which is advantageously formed in a portable type which is able to operate for a relatively long time with power supply from a battery.
According to the present invention, there is provided an apparatus for receiving broadcasting signals, which comprises a signal receiving portion for receiving a broadcasting signal carrying synchronous data, control information data and plural groups of program information data, a frequency converting portion for causing the broadcasting signal received by the signal receiving portion to be subjected to frequency conversion to produce an IF signal, an IF amplifying portion for amplifying the IF signal, an analog to digital converting portion for causing the IF signal derived from the IF amplifying portion to be subjected to analog to digital conversion to produce a digital IF signal, a digital demodulating portion for causing the digital IF signal to be subjected to digital demodulation processing, a program selecting portion for selecting one of plural groups of program information data obtained from the digital demodulating portion, an information reproducing portion for causing the program information data selected by the program selecting portion to be subjected to demodulation processing to reproduce program information, and an operation controlling portion operative to put at least each of the signal receiving portion, the frequency converting portion and the IF amplifying portion in a reduced power consumption state in periods other than a period in which portions of the broadcasting signal, which carry the synchronous data, the control information data and the program information data to be selected by the program selecting portion, respectively, are able to be received by the signal receiving portion.
In an embodiment of apparatus for receiving broadcasting signals according to the present invention, an automatic gain controller for supplying the IF amplifying portion with an automatic gain control signal is provided and the operation controlling portion is operative to cause the automatic gain controller to maintain a specific automatic gain control signal which is obtained just before an inoperative state of each of the signal receiving portion, the frequency converting portion and the IF amplifying portion when each of the signal receiving portion, the frequency converting portion and the IF amplifying portion is put in the inoperative state by the operation controlling portion.
In the apparatus for receiving broadcasting signals thus constituted in accordance with the present invention, in the periods other than the period in which the portions of the broadcasting signal, which carry the synchronous data, the control information data and the program information data to be selected by the program selecting portion, respectively, are able to be received by the signal receiving portion, at least each of the signal receiving portion, the frequency converting portion and the IF amplifying portion is controlled by the operation controlling portion to reduce power consumption.
Further, in the embodiment of apparatus for receiving broadcasting signals according to the present invention, the operation controlling portion is operative to put the analog to digital converting portion and the digital demodulating portion, in addition to the signal receiving portion, the frequency converting portion and the IF amplifying portion, in a reduced power consumption state in the periods other than the period in which the portions of the broadcasting signal, which carry the synchronous data, the control information data and the program information data to be selected by the program selecting portion, respectively, are able to be received by the signal receiving portion.
The operation controlling portion is operative, for putting the signal receiving portion, the frequency converting portion and the IF amplifying portion in the reduce power consumption state, for example, to cut off power supply to each of the signal receiving portion, the frequency converting portion and the IF amplifying portion in order to put each of the signal receiving portion, the frequency converting portion and the IF amplifying portion in the inoperative state or to control bias voltages supplied to the signal receiving portion, the frequency converting portion and the IF amplifying portion, respectively.
Further, the operation controlling portion is operative, for putting the analog to digital converting portion and the digital demodulating portion in the reduce power consumption state, for example, to cut off a clock signal supplied to each of the analog to digital converting portion and the digital demodulating portion in order to put each of the analog to digital converting portion and the digital demodulating portion in an inoperative state.
Accordingly, with the apparatus for receiving broadcasting signals according to the present invention, under a situation that at least each of the signal receiving portion, the frequency converting portion and the IF amplifying portion, in which power consumption is larger than that in any other portion, is put in the reduced power consumption state in the selected periods without hindrance in required operations, so that the whole power consumption in the apparatus is effectively reduced, the broadcasting signal carrying synchronous data, control information data and plural groups of program information data is received and desirous program information can be reproduced based on the program information data selected from the plural groups of program information data carried by the received broadcasting signal.
Especially, in the embodiment of apparatus for receiving broadcasting signals according to the present invention, when each of the signal receiving portion, the frequency converting portion and the IF amplifying portion is put in the inoperative state by the operation controlling portion, the automatic gain controller provided for supplying the IF amplifying portion with the automatic gain control signal is controlled to maintain the specific automatic gain control signal which is obtained just before the inoperative state of each of the signal receiving portion, the frequency converting portion and the IF amplifying portion. Further, in the embodiment of apparatus for receiving broadcasting signals according to the present invention, under a situation that the signal receiving portion contains an RF amplifier for amplifying the received broadcasting signal and the automatic gain controller is operative to supply the RF amplifier in the signal receiving portion, in addition to the IF amplifying portion, with the automatic gain control signal, the automatic gain controller is controlled to maintain the specific automatic gain control signal which is obtained just before the inoperative state of each of the signal receiving portion, the frequency converting portion and the IF amplifying portion when each of the signal receiving portion, the frequency converting portion and the IF amplifying portion is put in the inoperative state by the operation controlling portion.
Consequently, in this embodiment of apparatus for receiving broadcasting signals according to the present invention, when each of the signal receiving portion, the frequency converting portion and the IF amplifying portion having been put in the inoperative state is put again in operation, the automatic gain controller supplies the IF amplifying portion or the IF amplifying portion and the RF amplifier in the signal receiving portion with the specific automatic gain control signal obtained just before the inoperative state of each of the signal receiving portion, the frequency converting portion and the IF amplifying portion so that each of the signal receiving portion, the frequency converting portion and the IF amplifying portion becomes immediately stable in its operation.
As described above, with the apparatus for receiving broadcasting signals according to the present invention, the broadcasting signal carrying synchronous data, control information data and plural groups of program information data can be received and the desired program information can be reproduced based on the program information data selected from the plural groups of program information data carried by the received broadcasting signal with power consumption reduced effectively. Therefore, the apparatus for receiving broadcasting signals according to the present invention is advantageously formed in a portable type which is able to operate for a relatively long time with power supply from a battery.
The above, and other objects, features and advantages of the present invention will be become apparent from the following detailed description taken in conjunction with the accompanying drawings.